This invention relates to an ultrasonic debubbling method and apparatus therefor.
Generally, some kinds of liquids are required to be debubbled. For example, if a light-sensitive emulsion containing bubbles is coated onto a film material such emulsion cannot be used to form an uniform light-sensitive layer on the film. The emulsion is therefore required to be debubbled before it is coated onto the film material.
An example of an apparatus for debubbling, is disclosed in Japanese Patent Examined Publication No. 6365/1982. This apparatus comprises, as shown in FIG. 1, (a) heat-retaining chamber 100; (b) debubbling chamber 103 which is dipped in this heat-retaining chamber 100 and comprises, for example, primary cylinder 101 and secondary cylinder 102 which are connected with each other in the upper part of debubbling chamber 103; (c) pipe 104 for introducing a liquid to be debubbled and (d) pipe 105 for draining the liquid debubbled, which pipes are inserted from above into cylinders 101, 102 respectively so as to nearly reach the bottoms of the cylinders; and (e) ultrasonic transducer 106 arranged at the lower part of debubbling chamber 103. In this apparatus, debubbling is performed in such a manner that liquid to be debubbled is fed from pipe 104 for introducing the liquid to be debubbled into primary cylinder 101 until the liquid level reaches the upper part of cylinder 101 and then the upper part of secondary cylinder 102. Thereafter, the liquid flows down to pipe 105 for draining the debubbled liquid and is drained through pipe 105. During the entire process from introducing to draining the liquid, ultrasonic waves are radiated from ultrasonic transducer 106 to the liquid to be debubbled so as to force bubbles to rise up to the surface by applying an ultrasonic radiation pressure. In the drawing of FIG. 1, 107 is a float and 108 is an air-relief valve.
Increasing the ultrasonic energy in an ultrasonic debubbling process is one way to increase the debubbling efficiency per unit time, i.e., the debubbling capability of the apparatus of FIG. 1. However, in this apparatus, a liquid to be debubbled in both of cylinders 101, 102 is irradiated with ultrasonic waves by means of common ultrasonic transducer 106. Therefore, new bubbles are produced because of a cavitation effect when the ultrasonic energy is increased, so that bubbles produced in secondary cylinder 102 are drained upon suction into pipe 105. As a result, the liquid which should be debubbled in a debubbling process still contains bubbles. It is therefore unable to debubble satisfactorily.
In this apparatus, a particles of sediment in a sedimental particle-containing liquid such as silver halide in a light-sensitive silver halide emulsion are apt to deposit at to the bottoms of cylinders 101, 102, if the apparatus is used for a long time. Whenever debubbling chamber 103 is cleaned to remove such depositions, pipes 104, 105 should be detached from debubbling chamber 103, and debubbling chamber 103 is also detached from heat-retaining chamber 100. Therefore, the cleaning thereof becomes troublesome, particularly with a large-sized apparatus.